flutter_flutter/sky/engine/platform/fonts/FontDataCache.cpp

/*
 * Copyright (C) 2013 Google Inc. All rights reserved.
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 * modification, are permitted provided that the following conditions are
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 * in the documentation and/or other materials provided with the
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 * this software without specific prior written permission.
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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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#include "flutter/sky/engine/platform/fonts/FontDataCache.h"

#include "flutter/sky/engine/platform/fonts/SimpleFontData.h"

using namespace WTF;

namespace blink {

#if !OS(ANDROID)
const unsigned cMaxInactiveFontData = 250;
const unsigned cTargetInactiveFontData = 200;
#else
const unsigned cMaxInactiveFontData = 225;
const unsigned cTargetInactiveFontData = 200;
#endif

PassRefPtr<SimpleFontData> FontDataCache::get(
    const FontPlatformData* platformData,
    ShouldRetain shouldRetain) {
  if (!platformData)
    return nullptr;

  Cache::iterator result = m_cache.find(*platformData);
  if (result == m_cache.end()) {
    pair<RefPtr<SimpleFontData>, unsigned> newValue(
        SimpleFontData::create(*platformData), shouldRetain == Retain ? 1 : 0);
    m_cache.set(*platformData, newValue);
    if (shouldRetain == DoNotRetain)
      m_inactiveFontData.add(newValue.first);
    return newValue.first.release();
  }

  if (!result.get()->value.second) {
    ASSERT(m_inactiveFontData.contains(result.get()->value.first));
    m_inactiveFontData.remove(result.get()->value.first);
  }

  if (shouldRetain == Retain) {
    result.get()->value.second++;
  } else if (!result.get()->value.second) {
    // If shouldRetain is DoNotRetain and count is 0, we want to remove the
    // fontData from m_inactiveFontData (above) and re-add here to update LRU
    // position.
    m_inactiveFontData.add(result.get()->value.first);
  }

  return result.get()->value.first;
}

bool FontDataCache::contains(const FontPlatformData* fontPlatformData) const {
  return m_cache.contains(*fontPlatformData);
}

void FontDataCache::release(const SimpleFontData* fontData) {
  ASSERT(!fontData->isCustomFont());

  Cache::iterator it = m_cache.find(fontData->platformData());
  ASSERT(it != m_cache.end());
  if (it == m_cache.end())
    return;

  ASSERT(it->value.second);
  if (!--it->value.second)
    m_inactiveFontData.add(it->value.first);
}

void FontDataCache::markAllVerticalData() {
#if ENABLE(OPENTYPE_VERTICAL)
  Cache::iterator end = m_cache.end();
  for (Cache::iterator fontData = m_cache.begin(); fontData != end;
       ++fontData) {
    OpenTypeVerticalData* verticalData = const_cast<OpenTypeVerticalData*>(
        fontData->value.first->verticalData());
    if (verticalData)
      verticalData->setInFontCache(true);
  }
#endif
}

bool FontDataCache::purge(PurgeSeverity PurgeSeverity) {
  if (PurgeSeverity == ForcePurge)
    return purgeLeastRecentlyUsed(INT_MAX);

  if (m_inactiveFontData.size() > cMaxInactiveFontData)
    return purgeLeastRecentlyUsed(m_inactiveFontData.size() -
                                  cTargetInactiveFontData);

  return false;
}

bool FontDataCache::purgeLeastRecentlyUsed(int count) {
  static bool isPurging;  // Guard against reentry when e.g. a deleted FontData
                          // releases its small caps FontData.
  if (isPurging)
    return false;

  isPurging = true;

  Vector<RefPtr<SimpleFontData>, 20> fontDataToDelete;
  ListHashSet<RefPtr<SimpleFontData>>::iterator end = m_inactiveFontData.end();
  ListHashSet<RefPtr<SimpleFontData>>::iterator it = m_inactiveFontData.begin();
  for (int i = 0; i < count && it != end; ++it, ++i) {
    RefPtr<SimpleFontData>& fontData = *it.get();
    m_cache.remove(fontData->platformData());
    // We should not delete SimpleFontData here because deletion can modify
    // m_inactiveFontData. See http://trac.webkit.org/changeset/44011
    fontDataToDelete.append(fontData);
  }

  if (it == end) {
    // Removed everything
    m_inactiveFontData.clear();
  } else {
    for (int i = 0; i < count; ++i)
      m_inactiveFontData.remove(m_inactiveFontData.begin());
  }

  bool didWork = fontDataToDelete.size();

  fontDataToDelete.clear();

  isPurging = false;

  return didWork;
}

}  // namespace blink